Characterization of axenic isolates of Giardia intestinalis established from humans and animals in Germany
Giardia lamblia was adapted to grow in modified Diamond's TYI-S culture medium with a mean generation time of 12.0 +/- 1.1 hours. Addition of bovine or porcine bile to this medium dramatically promoted growth with marked reduction in generation time. The shortest mean generation time (7.5 hours) was obtained with fresh bovine bile and to our knowledge is the lowest reported time for axenically cultivated G. lamblia. Trophozoite numbers were increased by a factor of 3.4 after 48 hours cultivation. Generation time lengthened as bile concentration was increased, the effect being most marked with commercial bile preparations. We consider that this bile-supplemented TYI-S medium will support growth more consistently than the usual Giardia culture medium TPS-1, and is also cheaper. This trophic effect of bile on Giardia growth may partly explain why Giardia trophozoites are found mainly in the duodenum and proximal jejunum where bile is plentiful.